:28 RADIOGENESIS IN EVOLUTION. 



patterns " (to use the term applied by A. Bacot). The 

 actual facts of mutation are too big for that. 



Ample evidence has been provided by Bateson,* that 

 even specific distinctions frequently arise as single 

 variations. Nature leaps as well as creeps. Thus certain 

 meristic variations — or variations in symmetry and the 

 number of organs — may be frec[uently noted, and many 

 of these cannot develop through intermediate stages. 

 Thus, plants with a four-fold arrangement may jump to a 

 l^erfectly-developed five-fold form. Bateson also lays 

 stress on what he terms Homoeosis, or the variation 

 ■established when one organ takes on the character of 

 another organ, such as a disc floret of a composite flower 

 appearing in the likeness of a ray. Whatever may be 

 the opinion as to the operation of natural selection on 

 infinitesimal variations, there can be no question as to its 

 inevitable effects, preserving or exterminating, great steps 

 or mutations. The non-viable forms are ruthlessly stamped 

 out, and the fittest survive. 



Asa Gray believed that " variation has been led along 

 ■certain beneficial lines." To this and similar views the 

 name of Orthogenesis has been given. This term im])lies 

 .a guiding principle in variations, suggesting a proceeding 

 along certain definite lines. Plate uses the term 

 ectogenesis, or ectogenetic orthogenesis, for " definitely 

 directed variation." Naturally this view strongly aj)peals 

 to teleologists, and in certain philosojihical quarters, it 

 has been unwarrantably used. It is a very comfortable 

 sentiment and appeals to the popular imagination. But 

 when it comes to an inquiry into actual facts, it falls to the 

 ground. Bateson goes as far as to say that " no fragment 

 of real evidence can be produced in its support. "I 



There are, of course, other views of Orthogenesis. 

 Thus, Hans Gadow speaks of orthogenetic changes " as 

 predictable in their results as the river which tends to 

 shorten its course to the direct line from its head waters 

 to the sea. That is the river's "entelechy', and no more 

 due to purpose or design than is the series of improvements 



*" Materials for the Study of Variation," Macmillan, 1894. 

 t" Darwin and Modern Science,"" ]*. 101. 



